I have several ST devices, Nucleo boards, Discovery boards and standalone ST-LINK. One of my Windows 10 64 bit computer could not connect to devices with V2-1 (USB mass storage type). I use the newest firmware (updated on another computer), and the newest driver. I can see the device in the Device Manager, but the programs (IDEs, ST-LINK utility, etc) could not find it.
The older Discovery boards with V2 (without USB mass storage) and the standalone ST-LINK V2 works fine.

First one: Stlink V2-1 is never usable. Shows up in device manager, but none of the softwares can use it. Stlink V2 work fine.
Second and third: Works 6-8 times after Windows cold start. Then the same as with the first computer. Restart computer...
Fourth: No problems.

First one: Stlink V2-1 is never usable. Shows up in device manager, but none of the softwares can use it. Stlink V2 work fine.
Second and third: Works 6-8 times after Windows cold start. Then the same as with the first computer. Restart computer...
Fourth: No problems.

Assuming its not a hardware fault, you could always flash the V2 software onto your V2.1 board.

There is another thread about stlink hacking with a link to a blog where someone has figured out how to load alternative firmware versions onto the stlink by just changing the file names in stm's own java based updated.

Yes, it is not hardware problem. I think the USB mass storage is the problem. Driver confict? Antivirus? Windows drive indexing? Who knows...

Yes, this is the final solution: Downgrade V2-1 to V2-0. Works fine. On nucleo boards you have to short solder bridge 1 (USB power management), because the V2 firmware does not handle that well. No power for target when plugged in, just for and after upload.

vargham wrote:Thanks.
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I use 4 computers, all Win 10 64 bit, and the same development softwares. Newest Stlink driver and newest firmware. Same Avast antivirus on all.

First one: Stlink V2-1 is never usable. Shows up in device manager, but none of the softwares can use it. Stlink V2 work fine.
Second and third: Works 6-8 times after Windows cold start. Then the same as with the first computer. Restart computer...
Fourth: No problems.

vargham wrote:Yes, it is not hardware problem. I think the USB mass storage is the problem. Driver confict? Antivirus? Windows drive indexing? Who knows...

As a non-active, retired MCSE, I can relate to your frustration but you are doing yourself no favors by using 4 separate Win10 workstations and expecting them each to "work identically: with non-Microsoft software. Things do NOT work that way on windows because of the way the registry and Plug & Play subsystems work. Even if the 4 workstations are from the same shipment, same model h/w, same base configuration, the registry(s) on each four machines will take a life of its own after 1st use... adding software, removing software, p&p h/w detection, Win updates, etc.

My views are not popular with Microsoft, but here they are:
- If you use Microsoft tools to develop, turn of automatic update for the OS and other Microsoft products AND keep very good backups of all of your sources externally (just smart.) What you get is a Microsoft flavored world through rose-colored glasses. If things do not work as advertised, complain to M$.

- If you are using non-Microsoft tools and the vendor offers Linux flavors, then bite the bullet and get the hell off of the Microsoft OS platform. Your existing PC hardware will get a speed boost, memory utilization will improve, and ArduinoIDE and tools will have a far better development environment.